The effect of interfacial tension and emulsification in enhancing oil recovery during surfactant flooding

The effectiveness of various surfactants in improving crude oil displacement efficiency was evaluated using one-dimensional homogeneous core and three-dimensional heterogeneous models. Emulsification of the crude oil was simulated using an ultrasonic instrument, and the emulsification degree was evaluated based on droplet dispersion, droplet number density, interfacial tension, external phase viscosity, internal phase volume, and demulsification time. Six surfactants could be divided into five emulsifying types, non emulsification, emulsification inversion, early emulsification, late emulsification and whole process emulsification. The results showed that the surfactants had varying levels of effectiveness in improving displacement efficiency. The whole process emulsification system can effectively start the residual oil in the pore throat and reduce the free state and bound state residual oil saturation. The area of the mainstream zone between the injection and production wells was significantly expanded after the whole process emulsification system was injected. The whole process emulsification is more important than interfacial tension for enhancing oil recovery.